1. Field of the Invention
The present invention relates generally to improvements in a microwave oven and more particularly, pertains to a new and improved microwave oven sensing system wherein humidity and temperature sensors are positioned to sense the "in-situ" humidity and temperature environmental conditions in the microwave oven heating cavity of the microwave oven.
2. Description of the Prior Art
In the field of microwave ovens, it has been a general practice to sense environmental conditions of the microwave oven heating cavity in which foods are cooking with sensing devices which have been positioned external to the cavity, usually in an exhaust duct exiting from the microwave oven heating cavity to prevent electromagnetic interference to the sensors. Such sensing devices have been unsatisfactory in that the sensors, to operate properly, require a continuous flow of gas in the duct and therefore suffer from the dynamics of the gas flow in the duct system. Also, the response time and accuracy of the measurement by the sensors depended upon the degree of equilibrium reached in the exhaust duct system. Further, other factors affected the accuracy of the sensors such as the gas pressure and flow rate from the microwave oven heating cavity through the duct system to the outside environment, the diameter and length of the duct system itself, and the susceptibility of the sensor itself to large concentrations of pollutants in the gases being expelled from the oven cavity.
Prior art sensing systems have not been able to accurately measure temperature and more importantly, humidity, in an "in-situ" environment as the sensors which were located in the ducts for electromagnetic interference considerations were subject to large numbers of water molecules carrying grease and carbon particles from the wet, moist environment of the microwave oven heating cavity through the exhaust duct system to the outside environment. The sensors were not able to endure the water molecules and the exhausted gases from the hostile environment of the microwave oven heating cavity over extended time periods as sometimes, the temperature of the exhausted gases exceeded sixty to seventy degrees centigrade further degrading the sensors. As a result of the severe environmental conditions in the microwave oven heating cavity, the sensors would go out of calibration in addition to suffering from sensor degradation.
Past prior art humidity sensors have been of the variety such as lithium choloride humidity sensors which are affected by continuous abrupt humidity and temperature changes in addition to exposure to humidity saturation conditions. These sensors are further subject to concentration of gases, freons, sulfides, ozones, dioxides and monoxides, nitrogen, as well as saturated water vapor. These prior art humidity sensors further did not have long term stability in use and storage in addition to being subject to degradation from continued cycling over wide humidity ranges.
This invention, a microwave oven sensing system, overcomes the disadvantages of the prior art by providing an accurate sensing system of the "in-situ" humidity and temperature environmental conditions of the microwave oven heating cavity.